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"We will not be taking a backward step in addressing this issue. The rulings send a strong message to all of our tenants - Housing New Zealand will not tolerate criminal activity in its homes and we will move swiftly to end tenancies where it occurs," he said.

"The rulings also help ensure that the financial burden for remediation work does not fall to the taxpayer and we are being more vigilant than ever around retrieving costs from 'offending' tenants."

Housing NZ will involve other government bodies such as police and CYF when necessary.

Mr Commons said P-contamination also left vulnerable people on the social housing register with longer waits for accommodation while properties were cleaned

Sometimes that took up to three months.

Mr Commons said Housing NZ was considering testing all vacant state houses for P-contamination.

What the judgments say:

• The Ashburton tenant was ordered to pay $34,177.76 in costs, including: